Abstract: Objective　To investigate the effect and mechanism of astragaloside Ⅳ (AS-Ⅳ) regulating autophagy to reduce 5-fluorouracil (5-Fu) induced myocardial toxicity based on PINK1/Parkin signaling pathway in the rats. Methods　Thirty-six male SD rats aged 18 months were divided into control group, model group and AS-Ⅳ group by random number table method, with 12 rats in each group. The rat model was administered the intraperitoneal injection of 30 mg/kg 5-Fu every other day for 7 times. The intervention group was administered the intragastrical 20 mg/kg AS-Ⅳ diluent every day for 14 times. The serum levels of troponin I (cTnI), creatine kinase isoenzyme (CK-MB), myocardial mitochondrial ATP and membrane potential were measured. HE and Masson staining were used to evaluate the pathological changes of myocardium. The expression of microtubule-associated protein (LC3Ⅱ) was evaluated by immunofluorescence. The ultrastructure of mitochondria was observed under electron microscope. The protein expressions of PINK1/Parkin pathway (key molecules PINK1, Parkin, Beclin1, LAMP and LC3) were detected by Western blot assay. Results　Compared with the model group, AS-Ⅳ could slow down the weight loss (P＜0.05), reduce the secretion of myocardial enzyme cTnI and CK-MB (P＜0.05) and inhibit the decrease of mitochondrial ATP levels (P＜0.05). Compared with control group, the myocardial fibers were disorderly arranged and a large number of blue collagen fibers were deposited in the model group. After the intervention of AS-Ⅳ, the collagen volume fraction decreased in the model group (P＜0.05). Electron microscopy and LC3Ⅱ fluorescence labeling showed that after AS-Ⅳ intervention, the degree of mitochondrial damage was reduced and the expression of LC3Ⅱ was decreased (P＜0.05). Western blot results indicated that Beclin1, PINK1, Parkin, LAMP and LC3Ⅱ/Ⅰ expression levels were significantly reduced (P＜0.05). Conclusion　The 5-Fu induces myocardial mitochondrial injury and excessive cardiac mitochondrial autophagy, and AS-Ⅳ alleviates it by regulating autophagy 5-Fu myocardial toxicity. 

Key words: fluorouracil, Astragalin, mitochondria, autophagy, aging, cardiotoxicity, astragaloside Ⅳ, PINK1/Parkin signaling pathway